linux-kernel - Re: [PATCH v3 1/1] s390: virtio: let arch accept devices without IOMMU feature

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Date:   Wed, 17 Jun 2020 13:59:54 +0200
From:   Pierre Morel <pmorel@...ux.ibm.com>
To:     Heiko Carstens <heiko.carstens@...ibm.com>
Cc:     linux-kernel@...r.kernel.org, pasic@...ux.ibm.com,
        borntraeger@...ibm.com, frankja@...ux.ibm.com, mst@...hat.com,
        jasowang@...hat.com, cohuck@...hat.com, kvm@...r.kernel.org,
        linux-s390@...r.kernel.org,
        virtualization@...ts.linux-foundation.org, thomas.lendacky@....com,
        david@...son.dropbear.id.au, linuxram@...ibm.com, gor@...ux.ibm.com
Subject: Re: [PATCH v3 1/1] s390: virtio: let arch accept devices without
 IOMMU feature



On 2020-06-17 13:22, Heiko Carstens wrote:
> On Wed, Jun 17, 2020 at 12:43:57PM +0200, Pierre Morel wrote:
>> An architecture protecting the guest memory against unauthorized host
>> access may want to enforce VIRTIO I/O device protection through the
>> use of VIRTIO_F_IOMMU_PLATFORM.
>>
>> Let's give a chance to the architecture to accept or not devices
>> without VIRTIO_F_IOMMU_PLATFORM.
>>
>> Signed-off-by: Pierre Morel <pmorel@...ux.ibm.com>
>> Acked-by: Jason Wang <jasowang@...hat.com>
>> Acked-by: Christian Borntraeger <borntraeger@...ibm.com>
>> ---
>>   arch/s390/mm/init.c     |  6 ++++++
>>   drivers/virtio/virtio.c | 22 ++++++++++++++++++++++
>>   include/linux/virtio.h  |  2 ++
>>   3 files changed, 30 insertions(+)
>>
>> diff --git a/arch/s390/mm/init.c b/arch/s390/mm/init.c
>> index 6dc7c3b60ef6..215070c03226 100644
>> --- a/arch/s390/mm/init.c
>> +++ b/arch/s390/mm/init.c
>> @@ -45,6 +45,7 @@
>>   #include <asm/kasan.h>
>>   #include <asm/dma-mapping.h>
>>   #include <asm/uv.h>
>> +#include <linux/virtio.h>
>>
>>   pgd_t swapper_pg_dir[PTRS_PER_PGD] __section(.bss..swapper_pg_dir);
>>
>> @@ -161,6 +162,11 @@ bool force_dma_unencrypted(struct device *dev)
>>   	return is_prot_virt_guest();
>>   }
>>
>> +int arch_needs_virtio_iommu_platform(struct virtio_device *dev)
>> +{
>> +	return is_prot_virt_guest();
>> +}
>> +
>>   /* protected virtualization */
>>   static void pv_init(void)
> 
> Can we please stop dumping random code to arch/s390/mm/init.c?
> 
> All the protected virtualization functions should go into a separate
> file (e.g. mem_encrypt.c like on x86), some of which could also be in
> header files.
> 
> Please consider this a comment for the future.. just go ahead with
> this patch as-is.
> 

OK, thanks Heiko,
Pierre

-- 
Pierre Morel
IBM Lab Boeblingen